The present invention relates generally to the field of underground boring and, more particularly, to a method and apparatus for developing a bore plan.
Utility lines for water, electricity, gas, telephone and cable television are often run underground for reasons of safety and aesthetics. In many situations, the underground utilities can be buried in a trench which is then back-filled. Although useful in areas of new construction, the burial of utilities in a trench has certain disadvantages. In areas supporting existing construction, a trench can cause serious disturbance to structures or roadways. Further, there is a high probability that digging a trench may damage previously buried utilities, and that structures or roadways disturbed by digging the trench are rarely restored to their original condition. Also, an open trench poses a danger of injury to workers and passersby.
The general technique of boring a horizontal underground hole has recently been developed in order to overcome the disadvantages described above, as well as others unaddressed when employing conventional trenching techniques. In accordance with such a general horizontal boring technique, also known as microtunnelling, horizontal directional drilling (HDD) or trenchless underground boring, a boring system is situated on the ground surface and drills a hole into the ground at an oblique angle with respect to the ground surface. A drilling fluid is typically flowed through the drill string, over the boring tool, and back up the borehole in order to remove cuttings and dirt.
After the boring tool reaches a desired Depth, the tool is then directed along a substantially horizontal path to create a horizontal borehole. After the desired length of borehole has been obtained, the tool is then directed upwards to break through to the surface. A reamer is then attached to the drill string which is pulled back through the borehole, thus reaming out the borehole to a larger diameter. It is common to attach a utility line or other conduit to the reaming tool so that it is dragged through the borehole along with the reamer.
A common approach to planning a bore involves surveying a bore site and manually creating a bore plan on paper. Utilities and other underground objects are typically located and identified on the bore plan. Using the paper bore plan as a guide, the skilled machine operator attempts to direct the boring implement along the pre-planned boring route. A second operator periodically scans the drilling area to determine the actual location of the boring tool. Deviations between the planned and actual bore paths are resolved manually, the accuracy of which is highly dependent on the skill level of the machine and locator operators.
It can be appreciated that a manual approach to planning a bore and assessing the progress of the actual bore relative to a bore plan is problematic. Parameters such as entry angle, rod and product diameters, reamer diameter, rod bend radius, topography variations, utility diameter and safety clearance radius, grades, and minimum ground cover, for example, are generally not properly accounted for using conventional bore planning approaches. A bore plan that fails to properly accommodate these and other parameters is likely to be inaccurate, which may result in excessive drilling machine/pipe/bit wear and delay in completing the bore.
There exists a need in the excavation industry for an apparatus and methodology for automating the process of planning a bore. There exists a need for a bore planning approach that provides for greater accuracy than is currently attainable using existing approaches. The present invention fulfills these and other needs.